Development of thermoelectrically active and thermally sprayed ceramics

• Applicants: Dr. Manfred Fries; Professor Dr.-Ing. Christoph Leyens
• Subject Area: Glass, Ceramics and Derived Composites
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 289844451

The manufacture of economical thermoelectric generators (TEG) requires effective production technologies. Thermal spraying has the potential to be a cost-effective alternative for the production of TEGs, but major mechanical and technological challenges have to be addressed. TEG's can be realized by thermal spraying as a multi-layer system consisting of the thermoelectrically active p and n semiconductors, as well as electrically insulating and electrically conductive materials. The properties of the sprayed materials depend not only on the spray process but also on the quality of the feedstock material. While electrically insulating or conductive materials are well known in thermal spraying, thermoelectrically active materials have rarely been studied. The development of cost-effective TE materials is an urgent need for the production of TEGs. In particular for the processing by thermal spraying, in addition to the usual requirements concerning electrical and thermal conductivity and the Seebeck coefficient, the thermoelectric material should also be sprayable, have a low toxicity and be available in high amounts. Oxide materials have the highest potential to fulfill there requirements. However significant effort is required in order to understand the specific material behavior of these materials during the spray process and to improve their ZT values. Therefore, the focus of this project lies in the development of environmentally friendly and economically viable thermoelectric materials, which can be processed by thermal spraying. Doped zinc oxide is, due to its sprayability and promising thermoelectric properties, one of the most suitable oxide materials. The main goal of the project is the production of thermoelectrically active coatings which are mechanically stable, ca. 500 µm thick, and present a ZT of at least 0.3 at temperatures above 600 ° C. For this purpose, a tailored spray feedstock, in the form of powders and suspensions, has to be developed and manufactured, and the relationship between the process parameters of the different thermal spray methods and the coatings properties (Thermoelectric, structural, physical) has to be studied.

• DFG Programme: Research Grants